1. Field of the Invention
The present invention relates to an energy device and a method for producing the same.
2. Description of the Related Art
A lithium ion secondary battery includes a negative collector, a negative active material, an electrolyte, a separator, a positive active material, and a positive collector as main components. JP 5(1993)-43465 U discloses a lithium secondary battery wound in a spiral shape with a positive electrode placed inside.
In mobile equipment such as a mobile telephone and a personal digital assistant (PDA), there is a demand for a small secondary battery with a large capacity. For this purpose, a secondary battery formed thin in a plate shape is effective. However, the lithium secondary battery disclosed in JP 5(1993)-43465 U is a liquid-type secondary battery having a cylindrical shape, in which a spiral winding body is soaked in an electrolyte solution. Therefore, there is a limit to the miniaturization and the reduction in thickness of the liquid-type secondary battery due to its configuration.
Currently, the reduction in thickness and the increase in volumetric energy density (energy capacity per volume) of a lithium secondary battery are proceeding, and a lithium secondary battery with a thinner collector and a thinner active material, using a solid electrolyte, has been studied. According to this, it is expected that a high volumetric energy density is obtained even with a small thickness, and a separator is not required.
However, an energy element such as a lithium ion secondary battery requires several considerations and ideas for preventing a short-circuit. In the case where an energy element is made thinner, positive and negative electrodes are positioned close to each other, so that further considerations are required. For example, when a sheet-shaped energy element is wound in a plate shape for the purpose of the reduction in thickness and the increase in volumetric energy density, there is a possibility that a short-circuit may occur at a bent portion. Thus, some measures are required.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a thin energy device with a large capacity having a low short-circuit occurrence ratio and a method for producing the same.